The present invention relates to a process for preparing EDDN and/or EDMN by conversion of HCN and EDFA and/or EDMFA, wherein the conversion is effected in a reactor with limited backmixing and a short residence time. The present invention also relates to the preparation of TETA and/or DETA by conversion of the EDDN or EDMN thus prepared with hydrogen in the presence of a catalyst, wherein the preparation of EDDN or EDMN is followed by a depletion of water by distillation. The present invention further provides for the preparation of epoxy resins, amides or polyamides from the DETA or TETA obtained in accordance with the invention.
WO 2008/104579 and the prior art cited in WO 2008/104579 specify various preparation methods for EDDN and EDMN.
In WO 2008/104579, EDDN is prepared by reacting EDA with formaldehyde (FA) and hydrogen cyanide (HCN) with a molar ratio of EDA to FA to HCN of 1:1.5:1.5 to 1:2:2 [mol:mol:mol].
The preparation can be effected by a) reacting EDA with FACH with a molar ratio of EDA to FACH of 1:1.5 to 1:2, or b) preparing EDDN by reaction of an ethylenediamine-formaldehyde adduct (EDFA) with hydrogen cyanide with a molar ratio of EDFA to HCN of 1:1.5 to 1:2, or c) reacting EDA with a mixture of formaldehyde and hydrogen cyanide with a molar ratio of EDA to FA to HCN of 1:1.5:1.5 to 1:2:2, or d) reacting EDA simultaneously with formaldehyde and HCN with a molar ratio of EDA to FA to HCN of 1:1.5:1.5 to 1:2:2.
It is disclosed that these reactions are preferably performed at a temperature of 10 to 90° C. and at standard pressure to slightly elevated super-atmospheric pressure. Preferred reactors are described as being a tubular reactor or a stirred tank cascade. The reaction output formed is preferably worked up by distillation, first removing low boilers such as hydrogen cyanide in a first stage and removing water in a second distillation step. The remaining aminonitrile mixture may have a residual water content of preferably at least 10% by weight.
In the context of the present invention it has now been found that especially aqueous solutions of EDDN and EDMN are not thermally stable. EDDN and EDMN can form decomposition products which can reduce the yield of EDDN or EDMN and can lead in further reactions, for example the subsequent hydrogenation to give TETA and/or DETA, to a worsened processing quality, more particularly to an increase in discoloration.